A recent study by our group demonstrated that a 1-week infusion of insulin-like growth factor-I increases bile flow volume and bile acid secretion in rats, suggesting it is important in in vivo choleresis. In the present study, the effect in rats of a single administration of insulin-like growth factor-I on bile flow volume was investigated and compared with the choleretic drugs prednisolone and ursodeoxycholic acid. A significant and long-lasting increase in bile flow volume was observed in rats treated with insulin-like growth factor-I or prednisolone. Ursodeoxycholic acid significantly, but transiently increased. Combined treatment using insulin-like growth factor-I with prednisolone or ursodeoxycholic acid additively increased bile flow volume. Overall, this study demonstrated that the stimulatory effect of insulin-like growth factor-I on bile flow volume is almost equally potent to that of prednisolone and ursodeoxycholic acid, indicating the possible therapeutic potential of insulin-like growth factor-I in cholestatic liver diseases.